Radio circuit



July 19, 1932. M. J. CASTLE RADIO CIRCUIT Filed May 27, 1929 2 Sheets-Sheet l INVENTOR MELVIN JOHN CASTLE BY 1 l, Mu

ATTORNEY July 19, 1-932. CASTLE 1,867,808

RADIO CIRCUIT Filed May 27. 1929 2 Sheets-Sheet 2 3i i a @1 N\ F WWW A g P n] .J I v l1 -8 A g J noun F J Illk- 9 INVENTOR Z 3' 6 w MELVIN JOHN CASTLE R BY l/ j ATTORNEY :3 vided the improved Patented July 19, 1932 UNITED STATES PATENT OFFICE MELVIN JOHN CASTLE, OF SEATTLE, WASHINGTON, ASSIGNOB F ONE-HALF T0 WIL- LIAM I-I.

GERATY, OF SEATTLE, WASHINGTON RADIO CIRCUIT Application filed May 27,

This invention relates to improvements in radio circuits, and the principal object of the invention resides in the provision of an improved radio receiving circuit whereby more volume, finer selectivity and better tonal quality is produced than is ordinarily possible in radio receiving sets employing a far greater number of tubes; this result being accomplished in the present instance by a combined reflexing and regenerating action at both audio and radio frequency.

More specifically, the invention resides in the amplification of both radio frequency and audio frequency in a single alternating current screen grid tube.

Other objects of the invention reside in the details of connection and arrangement of parts as will hereinafter be described.

In accomplishing these objects, I have prodetails of construction, the preferred forms of which are illustrated in the accompanying drawings, wherein- Figure 1 is a diagrammatic illustration of a radio receiving set employing a circuit in accordance with the present invention.

Figure 2 is a diagrammatic illustration of a similar circuit employing an added intermediate radio frequency stage- Following through the wiring diagram of the receiving circuit, as disclosed in Figure 1:

Radio signals reaching the antenna, so marked, are brought through a circuit A to the primary winding of the radio frequency transformer L SW is an inductance switch which leads off of A, the purpose of which is to vary the inductance on the primary of coil L in accordance with the incoming frequency. G on secondary. of coil L isa .00035 microfarad condenser, the purpose of which is to eliminate any undesirable frequency. C", on coil L is a .01 microfarad condenser, the purpose of which is to protect the receiver from a possible short in the alternating current to the ground. The sig- 1929. Serial No. 366,304.

nal passes from coil combination L to primary winding of coil L where the energyis transferred to the secondary of L which is tuned by a .00035 microfarad condenser C This incoming signal is impressed upon the grid of tube V which is a screen grid type, A. (1-124. The output of this tube from the plate then travels through the primary winding of coil L then energy is transferred to the secondary of coil L and is brought into resonance, or tuned by G which is a .0005 microfarad condenser. This energy is impressed on the grid of V which is a type 127 A. C. tube, and is the detector. This signal is rectified and passed through the plate circuit RFC which is an .85 millihenry radio frequency choke coil, and this coil is by-passed by C which is a condenser of .002 microfarad capacity. The purpose of this condenser is to by-pass radio frequencies and prevent them from going into the primary circuit of AFT The rectified signal is transferred to secondary of AFT and passes through secondary of coil L at audio frequencies and is impressed on the grid of V screen grid 124 type tube. This audio signal is further amplified in V and passes through primary of L coil, where the audio signal is slightly refiexed, to V The audio signal, after passing through L primary, passes through RFC which is an .85 millihenry radio frequency choke coil. L primary and RFC is by-passed by C, which is a .001 microfaradcondenser. The audio signal then goes to primary of AFT3, which is of the high impedance primary type of transformer, and the signal is passed to grid circuit of V and amplified by V which is a UK 310 power tube. Thence, the audio signal goes to dynamic speaker input.

The combination of R and C is for the purpose of creating a grid bias of 1 volts on the grid of V The value of R is 1200 ohms. The capacity of C is .25 microfarad. RFC is a radio frequency choke coil of 1.5

' .5 microfarad capacity,

which is sensitive to weaker signals.

millihenries inductance. AF OX is an audio frequency choke coil of 3 henries inductance. RFC and AFCX is by-passed by C the capacity of which is .25 microfarad. C and is a filter circuit. C is a condenser of .0001 microfarad capacity. C is a condenser of .000003 to .00005 microfarad capacity. R is a non-inductive variable resistor, the range of which is 200 to 30,000,000 ohms resistance, the purpose of which is to regulate regeneration in this circuit and also to control and modulate volume as well. The audio signal then goes to the grid coil of L where the signal is further amplified, and super-regeneration takes place, which effect is obtained by imposing the super-audio oscillations which are produced by the windings of the transformer on the control grid of tube V This firsttube V really performs three different things, first, it amplifies the incoming frequency, second, it acts to a small de gree as a reflex audio amplifier, and third, it acts as an audio frequency oscillator.

The tubes employed in this circuit are, in

i the case of the circuit, Figure 1, a screen grid type A. C. 124; detector A. C. type, either 127 or 227; power amplifier CX 310.

R is a variable resistor or potentiometer, the value of which is 500,000 ohms. Thepurpose of this resistor is to regulate and control volume in V both at audio and radio frequencies. R is a 20 ohm potentiometer which, in connection with O which is of eliminates the sixty cycle hum on the tubes V and V R is a grid leak, the value of which is 3 megohms and G a grid condenser of .00025 microfarad capacity, and is a grid condenser in the grid circuit of the detector.

The dotted rectangle inclosing the coil L is a copper shield and is grounded at B. The purpose of this shield is to isolate this part of the circuit. Further, the primary of L V is variable to the secondary, the purpose of to vary the coupling between the primary and secondary and also to control the selectivity of the receiver. R is a variable resistor, the range of which is to megohms; the purpose of this resistor is to modulate the tone and regulate impedance. R

In Figure 2 is shown the same circuit as in Figure 1, except that L and V is an added, intermediate stage of radio frequency, the purpose of which is to make the receiver more The components of'this stage are as follows:

V is an A. C. 124 screen grid tube. L is a radio frequency transformer. C and C are two fiXed condensers, each of .0005 microfarad capacity. This is an untuned stage of radio frequency. 0 and C are two by pass condensers, of .25 microfarad capacity each. R is a 1200 ohm resistor. The purpose of the combination R and C is to furnish 1% volt grid bias for the control grid of V RFC is a 1.5 millihenry radio frequency choke coil. It is bypassed by C Lead is a source of plate current forV and connects to lead m. Lead '0 is a source of D. 0. current for screen grid V and is connected to movable arm of R and, in this case, R controls the volume in both V and V In Figure 1, a circuit for the radio receiving set has been shown in connection with a power pack, inclosed in a dotted rectangle C. SW is an alternating current toggle switch. P is a convenience outlet plug, or receptacle, the purpose of which is to connect the alternating current operated dynamic speaker. T is a filament transformer which furnishes filament current for V and V also PL which is a pilot light. S is a filament source for the two power rectifiers. V and V which are two 281 half wave rectifiers, furnish the direct current for the operation of the receiver. S is a secondary, or filament source for the power amplifying tube V R is a 150 ohm potentiometer, the purpose of which is to eliminate the sixty cycle hum from V PC and PC are two power chokes of henries inductance each. (1 is a 4: microfarad, C a 2 microfarad, and C a 4 microfarad fixed condenser. PO and P0. O C and C is a part of the filter system for the power pack. C is a condenser of 4 microfarad capacity. C is a 2 microfarad, C is a 1 microfarad and C is a 2 microfarad,- these condensers are a part of the filter system. R is a 7000 ohm, wire wound resistor, the purpose of which is to reduce the voltage to R which is a Truvolt voltage divider and the purpose of which is to obtain the various voltages required in the different plate circuits and screen grid V The leads from S of T, f and g, are connected to the filament circ it of V and V The leads from S of T 7L and j, are connected to the filament circuit of V Lead leads from maximum output of the power pack, which is 150 volts, to one side of the movable coil of the dynamic speaker. Lead 70 leads from R to R and to primary of AFT and has 60 volts D. O. Lead m, from is connected to primary of AFT and has 135 volts D- C. Lead 1", from R, is connected to C Lead 12 is the B negative leading from R to s, which is the negative and ground for the different components in the receiver.

The power pack is of the high voltage type, using two 281 rectifying tubes. The power amplifying stage may be one OX 310 tube, or two OX 310 or two OX 350 tubes used in a push pull system. 7

In Figure 2, the added intermediate radio frequency stage employs an alternating current screen grid tube, type 124;, same as V in Figure 1. V

In regard to grid leak in detector grid circuit, it may be desirable to connect the grid leak between the grid terminal and cathode terminal instead of across the grid condenser.

I claim:

1. A radio receiving system comprising a tuned antenna circuit, a radio frequency amplifying circuit coupled thereto and including a screened grid tube, a detector circuit coupled to the output of said amplifying circuit and including a thermionic tube, and means for reflexing output currents of said detector circuit through said amplifying circuit, including a variable non-inductive resistance for controlling said reflexed currents.

2. A radio receiving system comprising a tuned antenna circuit, a radio frequency amplifying circuit coupled thereto and including a screened grid tube, a. detector circuit coupled to the output of said amplifying circuit and including a thermionic tube, and means for refiexing output currents of said detector circuit through said amplifying circuit, including a variable non-inductive resistance for controlling said reflexcd currents, and means to feed back radio frequency currents from the output to the input of said amplifying circuit.

3. A radio receiving system comprising a tuned antenna circuit, a radio frequency amplifying circuit coupled thereto and including a screened grid tube, a detector circuit coupled to the output of said amplifying circuit, and including a thermionic tube, means for refleXing output currents of said detector circuit through said amplifying circuit, and means for regulating and controlling the intensity of said output currents.

4. A radio receiving system comprising a tuned antenna circuit, a radio frequency amplifying circuit coupled thereto and including a screened grid tube, a detector circuit coupled to the output of said amplifying circuit and including a thermionic tube, means for reflexing output currents of said detector circuit through said amplifying circuit, and means for regulating and controlling the intensity of said output currents comprising a variable non-inductive resistor.

5. A radio receiving system comprising a tuned antenna circuit, a radio frequency amplifying circuit coupled thereto, a screened grid tube in said amplifying circuit, whereby incoming frequencies will be amplified, a detector circuit coupled to the output of said amplifying circuit and including a thermionic tube, means for reflexing output currents of said detector circuit through said screened grid tube, and means to feed back high frequency currents from the detector circuit to said screened grid tube, whereby said tube will function as a reflex audio amplifier, and means including said screened grid tube to amplify audio frequency oscillations.

6. A radio receiving system comprising a tuned antenna circuit, amplifying circuits coupled thereto and including a single screened grid tube, a detector circuit coupled to said amplifying circuits and including a thermionic tube, and means for reflex ing output currents of the detector circuit through one of said amplifying circuits whereby said single screened grid tube will amplify both radio and audio frequencies.

Signed at Seattle, Washington, this 23rd day of April, 1929.

MELVIN JOHN CASTLE. 

